1. Field of the Invention
The present invention relates to an X-ray imaging apparatus.
2. Description of the Related Art
In X-ray fluoroscopic radiography, sensor driving is switched between moving image driving during shooting and still image driving when displaying still images. In an apparatus in which alignment of an X-ray generator and an X-ray sensor unit is performed by an operator, usually, alignment imaging is performed with a still imaging mode and serial imaging is performed with a moving imaging mode.
For example, Japanese Patent Laid-Open No. 2002-305687 discloses a technology in which multiple bias power sources are provided and bias voltage applied to a sensor is switched between the moving image mode and the still image mode. Japanese Patent Laid-Open No. 2002-305687 describes that a preparation period is provided to refresh a sensor in advance before a radiography period in which the charge generated through photoelectric conversion after X-ray exposure is read out so as to obtain one still image.
Moreover, Japanese Patent Laid-Open No. 2009-119021 discloses the technology of performing auxiliary imaging in which a subject is serially imaged with a reduced amount of radiation irradiated before performing main still imaging of the subject. Japanese Patent Laid-Open No. 2009-119021 discloses detecting periodicity of movement of the subject based on images obtained by the auxiliary imaging, generating pseudo images based on the periodicity, and calculating imaging parameters to be used in main still imaging based on these pseudo images.
Japanese Patent Laid-Open No. 2004-144713 discloses the technology of changing settings of pixel density depending on whether still images or moving images are formed based on read images. Japanese Patent Laid-Open No. 2004-144713 discloses that when still images are formed it is preferable to perform high pixel density reading in order to obtain high resolution images, and that when moving images are formed it is preferable to perform rapid low pixel density reading in order to secure the frame rate required of moving images.
When sensor driving is switched between still imaging and moving imaging, the sensor becomes unstable and correction errors occur at the time of switching. Therefore, conventionally, at the time of switching, standby time is needed until the sensor becomes stable. However, this standby time impairs usability for the operator.